To perform the study, Copley’s research team eliminated genes in Escherichia coli that code for critical enzymes. They then observed the bacteria reproducing over many generations to get a clear view of how the bacteria survived when given those limitations.
While the majority of enzymes have very specific functions that only work on one kind of chemical reaction, there are others that aren’t so specialized. These so-called ‘promiscuous’ enzymes might still be specific to one reaction but also have the ability to be flexible, boosting other reactions when conditions necessitate.
“We were rerouting metabolism,” explained Copley, a Professor of Molecular, Cellular and Developmental Biology at the University of Colorado Boulder.
A synthetic biologist at Harvard University, Betul Kacar, suggests that promiscuity could also give us a look into the past, showing us clues about what former roles and functions such enzymes may have had earlier in evolutionary history. An enzyme may be there to rescue the chemical reaction because catalyzing that reaction or one like it could have once been its primary job. “Trying to understand how novel pathways arise, what kind of mechanistic underlying forces shape those trajectories, is quite essential,” she explained.
Bacteria are able to formulate many kinds of alternative processes to make up for enzymes that are missing, depending on the environmental conditions they face, Copley noted. The most successful replacements are the efficient ones – reactions with fewer steps, or that can yield a larger amount of the necessary reaction product.
Sources: ScienceNews.org, 2nd American Society for Microbiology Conference on Experimental Microbial Evolution, University of Colorado Boulder